1. Field of the Invention
The present invention relates to a thrust reversing system for an aircraft, and more particularly to such a thrust reversing system particularly adapted for use with high bypass long duct fan engines.
2. Background Art
The design of effective thrust reversers has been a problem in the aircraft industry for a number of decades. Ideally, in the stowed configuration for cruise, the thrust reversing mechanism should be located so as to minimize any drag and also so as not to interfere with the operating components of the engine. This requirement is oftentimes incompatible with the need to provide effective reverse flow of the engine exhaust. The result is often a compromise between these two requirements.
Another problem is that some thrust reversers operate in such a way that at least part of the reversed flow is directed toward the ground so as to blow up dirt or small rocks which might then be drawn into the engine inlet. A related problem is that the reversed flow can be reingested back into the engine inlet. Further, many of the prior art thrust reversing mechanisms are expensive and have maintenance problems.
It is also desirable that the reversal of flow be accomplished in a manner that the reversed flow does not create any lift on the wing so as to take loads off the main gear or nose gears, and a corollary of this is that a desired feature of a thrust reversing system is to create greater loading on those gears. Another problem is that some thrust reversing mechanisms detract from the rudder and fin effectiveness of the aircraft.
A search of the patent literature has disclosed a number of patents related to thrust reversers, and these are recited below:
U.S. Pat. No. 3,262,271 (Beavers) shows a thrust reverser for a fan jet engine which reverses only the fan flow. There are plurality of isosceles-shaped flaps 22 which pivot from the fan cowl into the blocking position. This fan cowl section 19 moves rearwardly to expose vanes 38. The core exhaust is not reversed, and the exhaust appears to be uniformly reversed around the entire periphery of fan area.
U.S. Pat. No. 3,279,182 (Helmintoller) shows a thrust reversing system which is similar in principle to the Beavers patent discussed immediately above.
U.S. Pat. No. 3,483,702 (Ward) shows a thrust reverser having the same basic operating principles as the two patents noted immediately above (i.e., Beavers and Helmintoller). There are inner and outer flaps 26 and 25 which move to cause the thrust reversal, and there are guide vanes 44 that are attached to piston rods 40.
U.S. Pat. No. 3,600,394 (McClain) shows a thrust reverser operating to reverse the fan jet in accordance with the same operating principles as the three patents discussed immediately above. The doors 50 are pivotally mounted at 54 and are moved to the blocking position as section 28 moves rearwardly.
U.S. Pat. No. 3,608,314 (Colley) is another example of a thrust reverser having the same operating principles as the four discussed above. The reversing flaps 28 comprise the flap sections 30 and 32, and the aft section of the cowl moves rearwardly to uncover the vanes.
U.S. Pat. No. 3,660,982 (Goslan) shows a variety of thrust reversing arrangements somewhat schematically. In FIGS. 7 and 8, and also in FIGS. 13 and 14, there are shown reversing mechanism that deflect the thrust upwardly only. The patent is directed toward deflector plates positioned in the thrust reverser to prevent backflow into the bypass passageway.
U.S. Pat. No. 3,691,771 (Colley) discloses a thrust reverser where a plurality of blocker flaps 32 pivot radially inwardly to block the fan duct passageway of a fan duct engine, with the flow being deflected radially outwardly through the vanes 56 in a forward direction. (This arrangement is similar to the first five patents noted above).
U.S. Pat. No. 3,779,010 (Chamay et al) shows a thrust reverser where the aft section of the engine translates rearwardly to uncover a plurality of guide vanes which extend around the nozzle of the engine. This also causes a plurality of blocker flaps 70, which are pivotally mounted to the translating portion of the cowling, to move inwardly to a blocking position. A number of struts 86 interconnect the blocker flaps 70 with the engine casing 20. It is stated that this casing 20 could either house a conventional core engine, or it could be the plug of a core engine.
U.S. Pat. No. 3,844,482 (Stearns) shows a clam shell thrust reverser for an engine which is shown mounted directly to the wing. The clam shell panel 26 is pivotally mounted about a lower axis and rotates rearwardly and upwardly into its blocking position. An aft ramp segment 54 is pivotally mounted at a forward location at 48 and is rotated upwardly to block the rear opening of the clam shell panel 26 so that the exhaust flows into the clam shell panel 26 and is deflected forwardly and upwardly for thrust reversal.
U.S. Pat. No. 3,915,415 (Pazmany) shows a thrust reverser used on a wing mounted jet engine where the exhaust gases are discharged over the upper surface of the wing. The nacelle has an aft section 24 with a target blocker door 28 which is moved rearwardly and downwardly onto the upper surface of the wing into its thrust reversing position. A set of vanes is moved rearwardly toward the upper edge of the blocker door to deflect the exhaust gases upwardly and forwardly.
U.S. Pat. No. 3,917,198 (Sanders) shows a thrust reverser for a jet engine mounted to a wing where the exhaust gases are discharged over the upper surface of the wing. There is a deflector door 24 positioned at the aft end of the engine, and this is rotated upwardly and rearwardly to its thrust reversing position. The blocker door 22 has its forward edge moved rearwardly which, in turn, by the action of the linkage 48 moves the blocker door 22 upwardly into its blocking position to cooperate with the deflector door 24 to cause upward and forward deflection of the jet exhaust.
U.S. Pat. No. 3,981,463 (Pazmany) shows another thrust reverser for use in an engine mounted directly to a wing so as to discharge its exhaust over the upper surface of the wing. There is a blocker door 20 which is pivotally mounted at its forward end of the upper surface of the wing for movement upwardly and forwardly to its blocking position. A deflector door 30 is pivotally mounted at its rear end and movable upwardly and rearwardly to its thrust reversing position.
U.S. Pat. No. 4,073,440 (Hapke) shows a thrust reverser to reverse the thrust of both the primary and fan air. In some embodiments, blocker doors are arranged to be moved from a stowed position adjacent the inner circumferential wall defining the inside of the fan duct radially outwardly to a thrust reversal position, with the air flow through the fan duct being diverted radially outwardly through cascade vanes which are exposed by rearwardly translating an aft portion of the nacelle rearwardly. In some arrangements, blocker doors are also provided to move to a deployed position to divert the flow from the primary exhaust radially outwardly through cascade vanes, and in other arrangements, the primary flow is closed off, thus permitting the primary exhaust to exit through the nozzle through which the fan air is normally discharged.
U.S. Pat. No. 4,183,478 (Rudolph) shows a thrust reverser where in one embodiment there is a single clam shell door used in an engine which is mounted to the wing, with the exhaust being directed over the top surface of the wing. The door is slide mounted at a forward location, and is mounted by a pivot link at a rear location, this causing the door to have a rearward and angular movement to its thrust reversing position. Movement of the door exposes a set of cascade vanes. In another embodiment, two such clam shell doors are shown in an axisymmetric exhaust system.